Magna Carta is an English charter, originally issued in the year 1215, and reissued later in the 13th century in modified versions that omit certain temporary provisions, including the most direct challenges to the monarch's authority.

The charter first passed into law in 1225. The 1297 version, with the long title (originally in Latin) The Great Charter of the Liberties of England, and of the Liberties of the Forest, still remains on the statute books of England and Wales.

The 1215 Charter required King John of England to proclaim certain liberties, and accept that his will was not arbitrary, for example by explicitly accepting that no "freeman" (in the sense of non-serf) could be punished except through the law of the land, a right which is still in existence today.

Magna Carta was the first document forced onto an English King by a group of his subjects (the barons) in an attempt to limit his powers by law and protect their privileges. It was preceded and directly influenced by the 1100 Charter of Liberties, when King Henry I had specified particular areas where his powers would be limited.

Despite its recognised importance, by the second half of the 19th century nearly all of its clauses had been repealed in their original form. Three clauses remain part of the law of England and Wales, however, and it is generally considered part of the uncodified constitution. Lord Denning described it as "the greatest constitutional document of all times – the foundation of the freedom of the individual against the arbitrary authority of the despot". In a 2005 speech, Lord Woolf described it as "first of a series of instruments that now are recognised as having a special constitutional status", the others being the Habeas Corpus Act, the Petition of Right, the Bill of Rights, and the Act of Settlement.

The charter was an important part of the extensive historical process that led to the rule of constitutional law in the English speaking world, although it was "far from unique, either in content or form". In practice, Magna Carta in the medieval period did not in general limit the power of kings, but by the time of the English Civil War it had become an important symbol for those who wished to show that the King was bound by the law. It influenced the early settlers in New England and inspired later constitutional documents, including the United States Constitution.